Ignition system



April 25, 1944. P. c. SANDRETTO IGN ITION SYSTEM Filed Jude 19, 1942 I fzzaw mezz /fjawww Patents Apr. 25,, Edd

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AT FICE i HGNITION SYSTEM Peter G. Sandrctto, Gals. Park, 111., nor to United Air Lines, Ina. a corporation of melafllllpmdilltlflm remit, 1942, Serial No. 447,699

9 Claims.

In the usual ignition system employed with internal combustion engines, a source of lowcurrent, high-voltage energy is provided consistmg of a magneto or an induction coil excited by a battery. The high-voltage energy produced is tra .3 tted through a suitable rotating switch or distributor to the spark plugs associated with the cylinders of the engine. as is well known, the high-voltage energy thus' produced has a transient characteristic and lasts only for a short time interval. Due to the fact that the magneto or induction coil constitutes a high impedance device, the voltage delivered to the spark plug may be substantially decreased by any impedance shunted across the distributing system. Thus diificulties are encountered in shielding the various transmission lines or conductors leading to the spark plugs due to the fact that the capacity between the distributing wire and the shielding conduit constitutes a shunt impedance.

Shiel, however, is necessary due to the fact that the ignition voltage is nonsinusoidal, and therefore cannot be filtered from radio equipment associated with the vehicle. It has been found that if the low resistance shielding conduit-s,

and attempts have nmade to obviate or overcome these dimcultics by improvements in the types of shielding employed. It has also been prod to utilize individual step-up transformers associated with each of the spark plugs for the purpose-or localizing the high tension portions of the ition system. All of such proposed improvcments. however, have failed to provide a satisfactory ignition system, and it is a further object of this invention "to provide animproved ignition system which is substantially free from the shoot of shunt impedance, which does not produce 1* v w w in associated radio systems, which requires no shielding, and which, due to its particular characteristics, will be effective to increase the life oi the spark plugs to which it is applied.

In 2 5 out the invention in one form there is provided a low-voltage source of alternating current of substantially constant high frequency, together with siutable voltage-lncreasmg means located closely adjacent the spark plugs for producing at the spark plugs the high-voltage, high-frequency sparking current. The high 'irequency generated by the source is preferably so chosen that it will not overlap with the frequency used in radio communication equipment, and consequently the ignition system when applied to airplanes does not cause radio interference. Thelow-voltage transmission system extending from the source to the voltage increasing means is not appreciably attached by shunt impedance and requires no'shielding, and because 0! the location of the voltage-increasing means a relatively short or negligible length of highvoltage conductor is all that is required, and this negligible length of conductor can readily be protected from moisture.

For a more complete understanding of the invention reierence should now be had to the drawing, in which:

Fig. 1 is a diagrammatic representation of one form of ignition system embodying the present invention;

Fig. 2 is a diagrammatic representation of a low-voltage, high-frequency source which may be employed in the ignition system of Fig. 1; arid Figs. 3 and 4 are fragmentary diagrammatic representations of other .iorms of voltage-increasing means which may be utilized in the ignition system illustrated in Fig. 1.

Referring now to the drawing, the invention as shown in Fig. 1 is embodied in an ignition system comprising a source of low-voltage, highi'requency alternating current, which is represented as constituting an inductor-type, highfrequency alternator In, adapted to be driven at. a at speed from the internal combustion engine to which the system'is applied. Although any suitable driving arrangement may be provided, there is indicated, for purposes of illustration, a suitable constant speed clutch H, examples of which are well known in the art, the alternator ill being connected to the clutch it through a suitable shaft represented by a broken internal combustion engine (not shown) through a second shaft represented by the broken line l8. As shown, One terminal of the alternator I is connected toa ground through a conductor l4, and the other terminal of the alternator is connected through a suitable conductor Hi toa rotary switch or distributor l6. The distributor constitutes a simple rotary type switch having a plurality of fixed contacts adapted to be successively engaged by a co-operating contact. In the drawing only three stationary contacts ll, 18, and I8 are shown, adapted to be engaged by the rotating contact 20, but it will, of course, be understood that any desired number of stationary contacts corresponding to the number of cylinders in the combustion engine maybe employed. As indicated diagrammatically by the broken line 2|, the rotating contact 20 of the switch It may be driven from the internal combustion engine itself and serves in the usual manner to synchronize the ignition system with the movements of the engine pistons in their cylinders. The fixed contact I! of the rotary switch I6 is connected by a suitable low-voltage conductor 22 to one side of the primary winding 28 of a step-up transformer 24, which transformer 24 also includes a high-voltage secondary winding 25.- As shown, the other terminal of the primary winding 23 is connected through a conductor 26 to ground so as to complete the low-voltage circuit from the alternator l0, and one terminal of the secondary winding 25 is connected through a conductor 21 to a spark plug 26 which may be of the usual type, and which is associated with the corresponding cylinder of the internal combustion engine. The opposite terminal of the secondary winding 25 is also connected to ground, as shown. and the opposite terminal of the spark plug 28 is similarly connected to complete the secondary circuit of the transformer 24. I

While the transformer 24 is shown as being separate from the spark plug 28 in order to simplify the illustration thereof, it will be understood that the transformer is preferably mounted directly on the spark plug, or is at least located in proximity thereto so that the length of the conductor 21 will be negligible so far as its effect on line 2, and the clutch being connected to the of the magnitude encountered in normal ignition systems will not appreciably aifect the output voltage of the alternator. Furthermore, since the alternator produces substantially sinusoidal voltage, there will be no disturbance caused ih radio equipment operating on frequencies other than that employed in the ignition system. The alternator ||l may, for example, produce a irequency on the order of 50,000 cycles. Shielding of the low voltage conductors l5 and 22 is therefore un- I necessary. While only one spark plug and one In Fig. 2 there is illustrated another suitable source of low-voltage, high-frequency energy which may readily be employed with the improved ignition system of Fig. 1. This high frequency source comprises an electric discharge device or tube 3| connected to a resonant circuit comprising a condenser 82 and a pair of inductor coils 88 and 84, the adjacent terminals of which are connected by suitable by-passing condensers 35 and 86.

As shown, the tube 8| is energized from a suitable battery 81 and plate voltage for the tube 3| may be obtained from a motor generator set or dynamotor 38, which is illustrated as comprising a motor 39 connected for energization from the battery 81 and adapted to drive a generator 40, the output terminals of which are respectively connected tothe plate circuit of the tube 3| and to ground. I

With the circuit connections shown, the tube 3| will supply a high-frequency alternating current of relatively low voltage, the frequency of which depends upon the constants of the tube and the. circuit operation is concerned. Connected so directly across the terminals of the secondary winding 25 is a condenser 28, and as indicated diagrammatically by the arrow 30, either the inductance of the winding 26 or the capacity of the condenser 29 may be adjusted with relation to the frequency of the alternator III to produce a condition of parallel resonance in the secondary of the transformer. Thus a step-up in voltage of 100 or more can readily be attained with a transformer having small physical dimensions. While a separate condenser is illustrated, it will be understood that the necessary capacity for resoname may be supplied by the distributed capacity of the winding 26 and the capacity of the spark plug 28.

With the tuned, voltage-increasing means illustrated in Fig. 1 associated with the spark plug 28,

the oscillating circuit, and this low-voltage, highfrequency current may be supplied to the rotary switch l6 of Fig. 1 by means of a suitable conductor 4| connected to a tap on the coil 33. A blocking condenser 42 is inserted in the conductor 4| to prevent the flow of direct current to the remaining portions of the ignition system.

In Fig. 3 there is shown a somewhat different form of voltage-increasing means, which may be employed in place of the tuned transformer of Fig. 1, comprising a transformer 43 having a primary winding 44 and a secondary winding 45. As shown, the secondary winding 45 is connected directly across a spark plug 46, similar tothe spark plug 28 of Fig. 1, and it will be understood that the primary winding 44 is adapted to be connected to a rotary distributing switch and energized therefrom in the same manner as the primary winding 23 in Fig. 1.. Inthis embodiment of the invention, however, resonance in the'secondary winding of the transformer is obtained by providing a condenser 41 connected in series with the primary winding 44 and adapted to be tuned to cause resonance of the transformer at the frequency supplied from the source through the distributing switch. By reason of the resonance condition, a high voltage will be produced in the secondary winding of the transformer 43 and impressed across the spark plug 46.

In Fig. 4 the transformer is omitted and instead there is provided, for the purpose of obtaining a rise in voltage, a tuned circuit comprising a suitable coil 68, one terminal of which is connected through a conductor 5| and a suitable distributing switch (not shown) to the high-frequency, lowis connected through another suitable conductor 52 to a spark plug 53, the other terminal of the spark plug being grounded as in the system of Fig. 1. As shown, the terminal of the coil 50,

'which is connected to the conductor is also connected to one terminal of a suitable condenser 5d, the other terminal of which is connected to ground, and a second condenser 55 is connected across the coil 50 and the condenser 55, as shown.

The condenser 55 is a variable condenser and in order to provide a resonant rise in the voltage supplied over the conductor M, the condenser 55 is adjusted so that a condition of resonance attains.

' may be made, and it is contemplated, therefore,

by the appended claims to cover any such modii'ications as fall within the true spirit and scope of this invention.

Having thus described my invention, what I claim. and desire to secure by letters Patent is:

l. in an electrical ignition system for an internal combustion engine having sparking means associated with the cylinders thereof, the combination of a source of energy including means for generating low-voltage alternating current of at said sparking means a resonant rise in the voltage of said high-frequency current. I

4. In an electrical ignition system for an internal combustion engine having sparking means associated with the cylinders thereof, the combination of a source of energy including means for generating low-voltage alternating current of substantially constant high frequency, lowvoltage transmission means extending from said source to a point closely adjacent said sparking means, transformer means connected to said low' voltage transmission means at said point for energization from said source and for energize.- tion of said spar means, and means for tuning said transformer to resonance at said high frequency to supply to said sparking means ,a V

' ternal combustion engine having sparking means associated with the cylinders thereof, the combination of a source of energy including means for generating low-voltage alternating current of substantially constant high frequency, tuned circuit means connected to said sparking means,

substantially constant high frequency, low-voltage transmission means extending from said source to a point closely adjacent said sparking means, and voltage-increasing means connected to said transmission means for supplying to said sparking means a high-voltage sparking current at said substantially constant high frequency, said voltage-increasingmeans being positioned closely adjacent said sparking means.

2. In an electrical ignition system for an internal combustion engine having sparking means associated with the cylinders thereof, the combination of a source of energy including means for generating low-voltage alternating current of substanflally constant high frequency, lowvoltage transmission means extending from said source to a point closely adjacent said sparking means, and transformer means having a primary winding connected to said low-voltage transmission means at said point for energizetion from said source and having a. secondary winding for producing a high voltage current at said high frequency when said primary winding is energized from said source, said secondary winding being connected to impress said high and low-voltage trmsmission means extending from said source to said tuned circuit means including low-voltage switching means for periodically connecting said source to said tuned circuit means, said tuned circuit means being tuned to resonance at said high frequency to. efiect periodic energization of said sparking means at a high voltage and at said high frequency.

6. In an electrical ignition system for an internal combustion engine having sparking means associated with the cylinders thereof, the combination of a source of energy including means for generating low-voltage alternating current of substantially constant high frequency, transformer means located closely adjacent said sparking means and including primary and secondary circuits, low-voitage transmission means extending from said source to said transformer means including low-voltage switching means for periodically connecting said primary circuit to said source, means for tuning said secondary circuit to parallel resonance at said high frequency, and means connecting said tuned secondary circuit to said sparking means for periodic high-voltage energization of said sparking means at said high frequency.

7. In an electrical ignition system for an internal combustion engine having sparking means associated with the cylinders thereof, the combination of a source of ener comprising means for generating low-voltage alternating current of substantially constant high frequency and substantially uniform wave form, transformer means located closely adjacent said sparking means, low-voltage transmission means connecting said transformer means to said source, said transformer effecting a substantial voltage stepup at said sparking means, and means connecting said transformer to said sparking means for energization of said sparking means at a high voltage and at said high frequency.

8. In an electrical ignition system for an in ternal combustion engine having sparking means associated with the cylinders thereof, the combination of a source of energy comprising means for generating low-voltagealternating current of substantially constant high frequency and substantially uniform wave form, transformer means located closely adjacent said sparking means. and having a secondary winding connected thereacross, said transformer means having a primary winding, low-voltage transmission means connecting said primary winding for energization from said source, and means for tuning said transformer means to resonance at said high frequency to provide at said sparking means 5 a high-voltage high-frequency sparking current. 1 I 9. In an electrical ignition system for an in-' ternal combustion engine having sparking means associated with the cylinders thereof, the comsubstantially uniform wave form, tuned circuit means connected to said sparking means and located closely adjacent thereto, and low-voltage transmission means including low-voltage switchbination of a source of energy comprising means 1 ing means.

for generating low-voltage alternating current of substantially constant high frequency and PETER C. SANDRETI'O. 

